As an example of conventional battery modules, a battery module described in JP 2014-78366A (Patent Document 1 JP 2014-78366A) is known. This battery module has a structure in which a plurality of electric cells each including positive and negative lead terminals protruding outward from end portions thereof are stacked and adjacent lead terminals of opposite polarities are connected to each other, a pair of bus bars that are individually connected to those of the lead terminals connected in order that are located at opposite ends and that have mutually opposite polarities, and voltage detection terminals connected to terminal ends of voltage detection lines are individually connected for the lead terminals.